Ok, so it started working. Not sure why, all settings default, only changes are on the setup page:
Network set to static IP.
On the Event page:
'Server': set to SD card, named 'SD Card'.
'Media': set to 'Snapshot', source 1, 0 pre-event images,1 post-event images (possibly where I went wrong last time? Might've been set to 0) File name prefix 'Snapshot'.
'Event': enabled, named 'Snapshot', Trigger set to 'Periodic' with 1 minute intervals. (thinking I might change this to DI input and use something smarter to trigger images), 'Action' set to 'SD Card' with media 'Snapshot'.
'Recording': enabled.
Only other changes are to disable the IR illuminator and the LED status light. This doesn't work at night without a light always turned on. So I'm considering using a IR LED flash, but it needs to fire at the right moment. I might as well have a passive IR motion detector send a signal to both fire a flash and to the camera's DI input to record a frame as a JPEG. That will be later.